Monitoring the properties of coatings during the production process is a method to stabilize the process itself by ensuring the product quality in its early stage which enables the operator to optimize process parameters in real time. The paper will give a short overview of different methods to evaluate a coating during the production process (using color evaluation, physical model based and chemometric methods). In addition we will detail a cost effective measuring system for in-line and in-vacuo use. Setup: All methods described in the paper are based on the ThinProcess® WEB solution. These solutions are made possible by utilizing accurate measurements sensors with measurement capabilities which can be calibrated automatically during the production run. Methods: Different method to calculate or predict the coating thickness or coating weight will be shown in the paper. These methods can be combined to provide additional data for complex coatings. For simple layer designs, a correlation of the thickness and a color value may exist and this correlation needs to be found. The paper will show how this correlation is used to predict the coating thickness. Thickness results based on b* measurements. Additionally we will show how model based fits can be used to predict coating parameters like thickness.